The main folder of the Witcher 3 installation was open and I was checking out some of the extra stuff I downloaded in the !Downloads folder. I went back to the main folder and I noticed a folder named _redist, I opened it to see what it contained, and then went back to the main folder. While the main folder was still open, I launched the GOG galaxy client and the _redist folder suddenly disappeared. I clicked "back" but it said something along the lines of "this directory does not exist" etc. I verified the Witcher 3 game files through the GOG galaxy client, went back to check and the _redist folder is still missing. I launched the game and it starts up fine, no issues there, however I'm concerned whether I accidentally screwed something in the game files and will have problems down the line. I've provided a screenshot of my main folder. Any advice / similar experiences? Thanks in advance.

Same here, no _redist folder. And the game does not start. Yesterday evening run with no problem.

Missing mfc140u.dll file.
But this file is exist in /windows/system32 folder

I fixed it.
I uninstalled the Microsoft Visual C++ 2017 Redistributable 2017(x86) program, and installing the 2015(x86) version. Now working.

Thanks for your help!

Please help. My Witcher 3 game randomly stops working for no apparent reason. I've tried so many things and getting desperate. So I tried to uninstall the 2017 Microsoft Visual C++ and install the 2015 one, but it still doesn't launch. What did you do after installing the 2015 C++?

Thanks for your time

Uninstall all redists, and run these from powershell:

powershell -Command "(New-Object Net.WebClient).DownloadFile('https://download.microsoft.com/download/8/B/4/8B42259F-5D70-43F4-AC2E-4B208FD8D66A/vcredist_x86.EXE', 'vc_redist_2005_x86.exe')"
powershell -Command "(New-Object Net.WebClient).DownloadFile('https://download.microsoft.com/download/8/B/4/8B42259F-5D70-43F4-AC2E-4B208FD8D66A/vcredist_x64.EXE', 'vc_redist_2005_x64.exe')"
powershell -Command "(New-Object Net.WebClient).DownloadFile('https://download.microsoft.com/download/5/D/8/5D8C65CB-C849-4025-8E95-C3966CAFD8AE/vcredist_x86.exe', 'vc_redist_2008_x86.exe')"
powershell -Command "(New-Object Net.WebClient).DownloadFile('https://download.microsoft.com/download/5/D/8/5D8C65CB-C849-4025-8E95-C3966CAFD8AE/vcredist_x64.exe', 'vc_redist_2008_x64.exe')"
powershell -Command "(New-Object Net.WebClient).DownloadFile('https://download.microsoft.com/download/1/6/5/165255E7-1014-4D0A-B094-B6A430A6BFFC/vcredist_x86.exe', 'vc_redist_2010_x86.exe')"
powershell -Command "(New-Object Net.WebClient).DownloadFile('https://download.microsoft.com/download/1/6/5/165255E7-1014-4D0A-B094-B6A430A6BFFC/vcredist_x64.exe', 'vc_redist_2010_x64.exe')"
powershell -Command "(New-Object Net.WebClient).DownloadFile('https://download.microsoft.com/download/1/6/B/16B06F60-3B20-4FF2-B699-5E9B7962F9AE/VSU_4/vcredist_x86.exe', 'vc_redist_2012_x86.exe')"
powershell -Command "(New-Object Net.WebClient).DownloadFile('https://download.microsoft.com/download/1/6/B/16B06F60-3B20-4FF2-B699-5E9B7962F9AE/VSU_4/vcredist_x64.exe', 'vc_redist_2012_x64.exe')"
powershell -Command "(New-Object Net.WebClient).DownloadFile('https://download.microsoft.com/download/2/E/6/2E61CFA4-993B-4DD4-91DA-3737CD5CD6E3/vcredist_x86.exe', 'vc_redist_2013_x86.exe')"
powershell -Command "(New-Object Net.WebClient).DownloadFile('https://download.microsoft.com/download/2/E/6/2E61CFA4-993B-4DD4-91DA-3737CD5CD6E3/vcredist_x64.exe', 'vc_redist_2013_x64.exe')"
powershell -Command "(New-Object Net.WebClient).DownloadFile('https://download.microsoft.com/download/9/3/F/93FCF1E7-E6A4-478B-96E7-D4B285925B00/vc_redist.x86.exe', 'vc_redist_2015_x86.exe')"
powershell -Command "(New-Object Net.WebClient).DownloadFile('https://download.microsoft.com/download/9/3/F/93FCF1E7-E6A4-478B-96E7-D4B285925B00/vc_redist.x64.exe', 'vc_redist_2015_x64.exe')"
powershell -Command "(New-Object Net.WebClient).DownloadFile('https://download.visualstudio.microsoft.com/download/pr/100349138/88b50ce70017bf10f2d56d60fcba6ab1/VC_redist.x86.exe', 'vc_redist_2017_x86.exe')"
powershell -Command "(New-Object Net.WebClient).DownloadFile('https://download.visualstudio.microsoft.com/download/pr/100349091/2cd2dba5748dc95950a5c42c2d2d78e4/VC_redist.x64.exe', 'vc_redist_2017_x64.exe')"

call vc_redist_2005_x64.exe /Q
call vc_redist_2005_x86.exe /Q
call vc_redist_2008_x64.exe /Q
call vc_redist_2008_x86.exe /Q
call vc_redist_2010_x64.exe /Q
call vc_redist_2010_x86.exe /Q
call vc_redist_2012_x64.exe /Q
call vc_redist_2012_x86.exe /Q
call vc_redist_2013_x64.exe /Q
call vc_redist_2013_x86.exe /Q
call vc_redist_2015_x64.exe /Q
call vc_redist_2015_x86.exe /Q
call vc_redist_2017_x64.exe /Q
call vc_redist_2017_x86.exe /Q

del vc_redist_2005_x64.exe
del vc_redist_2005_x86.exe
del vc_redist_2008_x64.exe
del vc_redist_2008_x86.exe
del vc_redist_2010_x64.exe
del vc_redist_2010_x86.exe
del vc_redist_2012_x64.exe
del vc_redist_2012_x86.exe
del vc_redist_2013_x64.exe
del vc_redist_2013_x86.exe
del vc_redist_2015_x64.exe
del vc_redist_2015_x86.exe
del vc_redist_2017_x64.exe
del vc_redist_2017_x86.exe

echo Done
pause

Respect for managing to figure this out. However luckily I just did a clean reinstall, moved all my mods to another folder and added them back one by one to see which one was making the game fail to load. It was the "no rain mod", so I deleted it and now works fine. Sorry to see you go to so much trouble but I'm glad I can play again :)